Monitoring process for oxide removal

ABSTRACT

Generally, a method for monitoring a process of removing native oxides from an at least partially exposed layer disposed on a substrate is provided. In one embodiment, a method for monitoring includes disposing the substrate in a process chamber, exposing the at least partially exposed layer to a reactive pre-clean process, removing the substrate from the process chamber and measuring a sheet resistance of the exposed layer. In another embodiment, a method includes disposing the substrate in a process chamber, exposing the at least partially exposed conductive layer to a reactive pre-clean process that comprises an oxide reduction step, removing the substrate from the process chamber, contacting the conductive layer with one or more contact members, measuring a sheet resistance of the exposed conductive layer between the contact members, and comparing the measured resistance to a known value.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] Embodiments of the invention generally relate to a method formonitoring a process for pre-cleaning an at least partially exposedlayer disposed on a substrate.

[0003] 2. Background of the Related Art

[0004] Sub-quarter micron, multi-level metallization is one of the keytechnologies for the next generation of ultra large scale integration(ULSI). The multilevel interconnects that lie at the heart of thistechnology require planarization of interconnect features formed in highaspect ratio apertures, including contacts, vias, lines and otherfeatures. Reliable formation of these interconnect features is veryimportant to the success of ULSI and to the continued effort to increasecircuit density and quality on individual substrates and die.

[0005] The increase in circuit densities primarily results from adecrease in the widths of vias, contacts and other features as well as adecrease in the thickness of dielectric materials between thesefeatures. Cleaning of the features to remove contaminants prior tometallization is required to improve device integrity and performance.The decrease in width of the features results in larger aspect ratiosfor the features and increased difficulty in cleaning the features priorto filling the features with metal or other materials. Failure to cleanthe features can result in void formation within the features or anincrease in the resistance of the features. Therefore, there is a greatamount of ongoing effort being directed at cleaning small featureshaving high aspect ratios, especially where the ratio of feature widthto height is 3:1 or larger.

[0006] The presence of native oxides and other contaminants within asmall feature contributes to void formation by promoting unevendistribution of a depositing material such as metal. Regions ofincreased growth merge and seal the small features before regions oflimited growth can be filled with the depositing metal. Native oxidesform within the features when a portion of a layer (or sublayer), suchas silicon, aluminum, or copper, is exposed to oxygen in the atmosphereor is damaged during a plasma etch step. Other contaminants within thefeatures can be sputtered material from an oxide over-etch, residualphotoresist from a stripping process, leftover polymer from a previousoxide etch step, or redeposited material from a sputter etch process.

[0007] The presence of native oxides and other contaminants also canreduce the electromigration resistance of vias and small features. Thecontaminants can diffuse into the dielectric layer, the sublayer, or thedeposited metal and alter the performance of devices that include thesmall features. Although contamination may be limited to a thin boundaryregion within the features, the thin boundary region is a substantialpart of the small features. The acceptable level of contaminants in thefeatures decreases as the features get smaller in width.

[0008] Pre-cleaning of features to remove native oxides and othercontaminants has become increasingly utilized to prepare surfaces forbarrier layer or metal deposition. One process for removing nativeoxides and other contaminants from polysilicon, copper and metalsurfaces is described in U.S. Pat. No. 6,107,192, issued Aug. 22, 2000to Subrahmanyan et al., which is hereby incorporated by reference in itsentirety. This process, which may be performed in a REACTIVE PRE-CLEAN™II process chamber, available from Applied Materials, Inc., of SantaClara, Calif., generally includes a first cleaning step and a secondreducing step. The cleaning step features a soft plasma etch using areactive gas such as oxygen, a mixture of CF₄/O₂, or a mixture ofHe/NF₃, wherein the plasma is preferably introduced to the chamber froma remote plasma source. The remaining native oxides are then reduced inthe second step by treatment with a hydrogen comprising plasma.

[0009] Typically following the first or both pre-cleaning steps, thefeatures can be filled with metal by available metallization techniqueswhich typically include depositing a barrier/liner layer on exposeddielectric surfaces prior to deposition of aluminum, copper, ortungsten. The pre-cleaning and metallization steps can be conductedremotely or preferably on integrated processing platforms, such as thefamily of ENDURA®, PRODUCER® and CENTURA® processing platforms, allavailable from Applied Materials, Inc., of Santa Clara, Calif.

[0010] As the removal of native oxide and other contaminants directlyenhance device performance, monitoring of the effectiveness of thepre-clean process is advantageous to ensure robust process chamberperformance. Typically, pre-clean processes are monitored by takingreflectivity measurements of the exposed layer on the substrate. As thepresence of oxides and other contaminants on the oxide layer directlychanges the reflectivity of the exposed layer, the measured reflectivityis an indicator of the presence of native oxides or other contaminantson the exposed surface of the substrate. Reflectivity is typicallymeasured in pre-clean processes using optical devices. Generally, a beamof light is reflected off the substrate surface to the sensor. As thereflectivity of the exposed film is indicative of the composition of thefilm (i.e., whether contaminants or native oxides are residing on thesurface) the cleanliness of the film can be determined.

[0011] However, when using optical devices to measure reflectivity of amaterial, care must be taken not to introduce measurement errors. Forexample, focal distance between the sensors and the substrate, which areeasily disturbed, must be maintained. This results in a need tofrequently calibrate the measurement system. Additionally, the beamgenerator and sensor are sensitive to contamination on their lenses.Moreover, the surface roughness of the film, which could be changed bythe pre-clean process, may affect the reflectivity by changing therefraction characteristics of the surface. Thus, as the demand forsmaller feature sizes increases the importance of the elimination ofcontaminants and native oxides from the exposed surfaces, a more robustmeasuring system is needed to ensure robust and efficient pre-cleaningprocesses.

[0012] Therefore, there is a need for an improved method forpre-cleaning an at least partially exposed layer disposed on asubstrate.

SUMMARY OF THE INVENTION

[0013] In one aspect of the invention, a method for monitoring a processof removing native oxides from an at least partially exposed layerdisposed on a substrate is provided. In one embodiment, a method formonitoring a process of removing native oxides from an at leastpartially exposed layer disposed on a substrate includes disposing thesubstrate in a process chamber, exposing the at least partially exposedlayer to a reactive pre-clean process and measuring a sheet resistanceof the exposed layer.

[0014] In another embodiment, a method for monitoring a process ofremoving native oxides from an at least partially exposed conductivelayer disposed on a substrate includes disposing the substrate in aprocess chamber, exposing the at least partially exposed conductivelayer to a reactive pre-clean process that comprises an oxide reductionstep, removing the substrate from the process chamber, contacting the atleast partially conductive layer with one or more contact members,measuring a sheet resistance of the at least partially exposedconductive layer between the contact members, and comparing the measuredresistance to a known value.

[0015] In yet another embodiment of the invention, a method formonitoring a process of removing native oxides from an at leastpartially exposed conductive layer disposed on a substrate includesdepositing a copper seed layer on a sample substrate in a first chamber,exposing the copper seed layer to a reactive pre-clean process in asecond chamber to remove native oxides from the copper seed layer,transferring the sample substrate from the second chamber to a metrologydevice, measuring the sheet resistance of the conductive layer, andcomparing the measured sheet resistance to a known value.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] So that the manner in which the above-recited features,advantages and objects of the present invention are attained can beunderstood in detail, a more particular description of the invention,briefly summarized above, may be had by reference to the embodimentsthereof which are illustrated in the appended drawings.

[0017] It is to be noted, however, that the appended drawings illustrateonly typical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

[0018]FIG. 1 depicts a flow diagram of one embodiment of a method formonitoring a process for removal of oxides from an exposed layerdisposed on a substrate;

[0019]FIG. 2 is sectional view of one embodiment of a pre-clean chamber;and

[0020]FIG. 3 is a schematic diagram illustrating oxide growth andremoval on a substrate;

[0021]FIG. 4 is a schematic diagram illustrating one embodiment of amethod of measuring the resistance of the exposed layer of thesubstrate.

[0022]FIG. 5 is a schematic depicting one configuration of probesarranged to measure resistance on a substrate;

[0023]FIG. 6 is one embodiment of a processing system having a pre-cleanchamber; and

[0024]FIG. 7 is sectional view of another embodiment of a pre-cleanchamber.

[0025] To facilitate understanding, identical reference numerals havebeen used, wherever possible, to designate identical elements that arecommon to the figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] Generally, a method for monitoring a process for removal ofnative oxides from an exposed layer disposed on a substrate is provided.FIG. 1 depicts a flow diagram of one embodiment of a method 100 formonitoring a process for removal of native oxides from an exposed layerdisposed on a substrate that includes a step 102 of disposing asubstrate having an exposed layer in a process chamber, a step 104 ofexposing the layer to a reactive pre-clean process, a step 106 ofremoving the substrate from the process chamber, and a step 108 ofmeasuring the resistance of the layer. Although the preferred embodimentof the method 100 is described below with reference to an illustrativeprocess chamber performing one embodiment of a pre-clean process toremove native oxides from an exposed copper layer, the inventivemonitoring method may be effectively applied in other chambers and whileusing other processes on other types of exposed materials (ie., otherconductors and semiconductors). Generally, the inventive method may bepracticed with production substrates through a sampling regime.Alternatively, utility substrates, prepared with an native oxide grownover an exposed material of interest, may be periodically sampled duringprocessing of production substrates.

[0027]FIG. 2 depicts a cross sectional view of one embodiment of achamber 40 in which steps 102, 104 and 106 may be practiced. The chamber40 is preferably a dual frequency etch chamber such as the Pre-Clean IIChamber available from Applied Materials, Inc., of Santa Clara, Calif.Generally, the chamber 40 comprises an enclosure 72, a substrate support42 disposed within a processing region of the chamber 40, an RF powersource 74 connected to an inductive coil 98 disposed outside theenclosure 72 and a power source 80 connected to the substrate support 42through a mating circuit 38.

[0028] The enclosure 72 includes side walls 82, a bottom 84 and a top86. An access port 34 is generally disposed in the side walls 82 toallow entry and egress of the substrate 54 from the chamber 40. The port34 is selectively sealed by a slit valve 36 to isolate the processregion 90 during processing. One slit valve that may be used toadvantage is described in U.S. Pat. No. 5,226,632, issued Jul. 13, 1993to Tepman, et al., which is hereby incorporated by reference in itsentirety. A substrate handling robot utilized to pass the substratethrough the port 34 and place the substrate on the substrate support 42are generally known and have been omitted for the sake of clarity.

[0029] A quartz dome 88 is disposed under the top 86 and above theprocessing region 90. The quartz dome 88 is typically part of a “processkit” that is replaced after a certain number of substrates have beenprocessed in the chamber 40. The inductor coil 98 is generally disposedaround the quartz dome 88 and connected through a matching circuit 32 tothe RF power source 74. The RF power source 74 inductively couples powerto a plasma formed within a processing region 90 during processing. Thecoil 98 may be vertically stacked about the dome 88 as shown in FIG. 1,disposed equidistant from the dome or disposed in other configurations.

[0030] A processing gas supply 92 is coupled to a gas inlet 76 disposedin the chamber 40 and introduces the process and/or other gas(es) intothe process region 90 of chamber 40 during processing. A gas exhaust 78in fluid communication with the process region 90 evacuates the chamber40 prior to processing. A throttle valve 94 and a vacuum pump 96 coupledto the exhaust port maintain a predetermined pressure within the processregion 90 of the chamber 40 during processing.

[0031] The substrate support 42 generally comprises a pedestal 44disposed within a recess 46 on a top surface 50 of a quartz insulatorplate 48. The top surface 50 of the pedestal 44 extends slightly higherthan the upper annular surface 52 of the quartz insulator plate 48 andis in contact with a central portion of the bottom surface or backside58 of the substrate 54. The pedestal 44 is connected to the power source80 that electrically biases the pedestal 44 during processing. Theperipheral portion of the substrate 54 extends above the upper annularsurface 52 of the quartz insulator plate 48 and forms a gap 56 betweenthe bottom surface 58 of the substrate 54 and the upper annular surface52 of the quartz insulator plate 48. Optionally, the substrate support42 includes a temperature controller or a heater (not shown) to controlthe temperature of the substrate during processing.

[0032] In one mode of operation, the substrate 54 having an at leastpartially exposed metal layer (see the copper layer 304 of FIG. 3) ispassed through the port 34 and positioned on the substrate support 42 atstep 102. The slit valve 36 is closed and the processing region 90 ofthe chamber 40 is evacuated.

[0033] At step 104, a processing gas comprising a reactive gas that isoften combined with an inert gas is introduced through the gas inlet 76into the processing region 90. Examples of inert gases that may beutilized include helium, argon, nitrogen and other non-reactive gases.Typically, the reactive gases include hydrogen, particularly forprocessing copper, however, other gases may be utilized including oxygenand fluoride comprising gases. In one embodiment, the processing gasincludes helium mixed with about 5 percent or less hydrogen. Typically,the processing gas is flowed into the chamber at between about 10 sccmand about 1000 sccm, and preferably, at about 100 sccm.

[0034] To activate the reaction, a plasma is formed from the processinggas in the processing region 90 through inductive coupling and/orcapacitive coupling. The initial plasma is preferably struck by biasingthe substrate support 42 between about 1 W and about 100 W and betweenabout 100 KHz and about 100 MHz for about 3 seconds. Alternatively, theinitial plasma is generated by applying power to the inductive coil 98or by other ignition methods or devices.

[0035] During the reduction reaction period, the inductive coil 98 isbiased between about 1 W and about 1000 W at between about 100 KHz andabout 60 MHz while the substrate support 42 is biased between about 0 Wand about 100 W. Alternatively, during the reduction reaction period,the plasma in the processing region 90 is sustained solely by theinductive coil 98. Alternatively, the plasma within the processingregion 90 may be excited and sustained during processing by inductivecoupling only, capacitive coupling only or combinations of bothinductive and capacitive coupling.

[0036] During processing, the chamber pressure is preferably maintainedbetween about 20 mTorr and about 100 mTorr by controlling theopen/closed state of the throttle valve 94. A number of operatingparameters are adjusted to eliminate sputtering of the copper nativeoxides by the ions in the plasma and to maximize the reduction reaction.These operating parameters include the power supplied to the inductivecoil and the substrate support, the hydrogen concentration and flow rateof the processing gas, the pressure within the processing region 90, andthe density of the resulting plasma. Optionally, the temperature of thesubstrate 54 during processing is controlled by a temperature controldevice (not shown) within the substrate support 42 to enhance or toactivate the reduction reaction for some metal native oxides. However,for the reduction reaction of copper native oxide, it is not necessaryto heat (or cool) the substrate 54 to a particular temperature.

[0037]FIG. 3 schematically illustrates the substrate 54 having an atleast partially exposed copper layer 304 such as a PVD seed layer thatincludes a film of copper native oxide 306 undergoing a reductionprocess. During the reduction reaction process, the hydrogen ions withinthe plasma react with the copper native oxide 306 to form metalliccopper and water vapor as follows:

[0038] Cu₂O+H₂→2Cu +H₂O (vapor)

[0039] The chemical reaction reduces the copper native oxide 306 andleaves metallic copper where the copper native oxide previouslyoccupied. Thus, no sputtering of the copper native oxide occurs duringprocessing, and no unwanted copper native oxide is left within theinterconnect feature.

[0040] Returning to FIG. 2, preferably after the desired processing timeand the reduction of copper native oxide to copper, the power to theinductive coil 98 is continued, and the power supplied to the substratesupport 42 is reduced to about 1 W. This step reduces particlegeneration as the reduction reaction period ends. Subsequently, theservo control throttle valve 94 is opened fully, and the powers suppliedto the inductive coil 98 and substrate support 42 are turned off. Theprocess gas flow over the substrate 54 is then increased to perform afinal substrate surface conditioning step to reduce any static chargesthat may have built up during the process. After the final conditioningstep, the processing gas supplied into the chamber 40 is shut off, andthe chamber 40 is evacuated of the remaining processing gas and processby-products. The substrate 54 is then transferred out of the chamber 40at step 106.

[0041]FIG. 4 depicts a simplified schematic of one embodiment of ametrology device 400 that may be adapted to practice step 108 of theinvention. Generally, the metrology device 400 includes one or moreprobe sets 410 that may be placed in contact with the exposed layer 306of the substrate 54. In one embodiment, each probe set 410 includes afirst contact pin 402, a second contact pin 404 and a resistance meter406 coupled therebetween. The first and second contact pins 402, 404 aredisposed in a predetermined spaced-apart relation 412. As the contactpins 402, 404 are placed in contact with the exposed layer 304, a points480A and 480B on the substrate 54, the resistance across the knowndistance 412 of the layer 304 is determined. The measured resistance maybe compared with known sheet resistance values for copper. By comparingthe actual resistance value with the known sheet resistance for thematerial comprising the layer 304, the level of contamination (such asremaining native oxides 306) may be determined. Examples of metrologydevices which may be adapted to benefit from the invention are availablefrom EDTM, Inc, of Toledo, Ohio, Creative Design Engineering, andKLA-Tencor of San Jose, Calif. Using this information, the effectivenessof the pre-clean step 104 may be monitored.

[0042] In another embodiment, the probe sets 410 are coupled to acontroller 482. The controller 482 generally includes a centralprocessing unit (CPU) 484, support circuits 488 and memory 486. The CPU484 may be one of any form of computer processor that can be used in anindustrial setting for controlling various chambers and subprocessors.The memory 486 is coupled to the CPU 484. The memory 486, orcomputer-readable medium, may be one or more of readily available memorysuch as random access memory (RAM), read only memory (ROM), floppy disk,hard disk, or any other form of digital storage, local or remote andgenerally stores or has access to the known sheet resistance values. Thesupport circuits 488 are coupled to the CPU 484 for supporting theprocessor in a conventional manner. These circuits include cache, powersupplies, clock circuits, input/output circuitry, subsystems, and thelike. The controller 482 may take the place of the meters 406 for eachprobe set 410.

[0043] Generally, the controller 482 receives the resistance valuesobtained by the probe sets 410 and provides additional processinformation. For example, the probe sets 410 may be distributed acrossthe substrate's surface and the resistance data may be used to providean average sheet resistance. Alternatively, as depicted in FIG. 5, theprobe sets 410 may be arranged in sub-groups, for example, a centergroup 502 and a perimeter group 504 disposed radially relative thecenter group 502, to determine the effectiveness of the process in onelocation relative another. The center and perimeter groups 502, 504 mayeach comprise one or more probe sets 410.

[0044] Referring to FIG. 6, a schematic diagram shows an integratedprocessing system 660 having a pre-clean chamber 672 for pre-cleaning ofthe substrates and both PVD and CVD chambers thereon in which integratedmetallization processes can be implemented. The processing system 660generally includes a transfer chamber 690 that is surrounded by aplurality of process chambers. Typically, the substrates are introducedand withdrawn from the processing system 660 through a cassette loadlock662.

[0045] In one embodiment, the transfer chamber 690 includes a firstbuffer chamber 668 and a second buffer chamber 680. A first robot 664having a blade 667 is located within the first buffer chamber 668. Thefirst robot 664 transfers substrates between the cassette loadlock 662,degas wafer orientation chamber 670, remote plasma source pre-cleanchamber 672, HP-PVD Ti/TiN chamber 675 and a cooldown chamber 676 whichare disposed adjacent to the first buffer chamber 668. A second robot678 is located in the second buffer chamber 680 and facilitates thetransfer of substrates to and from the cooldown chambers 676, a PVD IMPTi/TiN chamber 682, a CVD Al Chamber 684, a CVD TiN chamber 686, and aPVD HTHU Al chamber 688. Of course other process chambers may besubstituted.

[0046] The second buffer chamber 680 in the integrated system ispreferably maintained at low pressure or high vacuum in the range of10⁻⁸ torr. The specific configuration of the chambers illustrated inFIG. 6 comprises an integrated processing system capable of both CVD andPVD processes in a single cluster tool. This particular chamberconfiguration or arrangement is merely illustrative and moreconfigurations of PVD and CVD processes are contemplated by the presentinvention.

[0047] Generally, substrates are transferred between the first andsecond buffer chambers 668 and 680 through a cooldown chamber 676. Othertransfer chambers 690 may be configured combining the buffer chambers668 and 680 into a single chamber having a platform disposed therein tofacilitate handoff of substrates between the robots 678 and 664, anexamples of which is the ENDURAO SL processing platform, available fromApplied Materials, Inc., Santa Clara, Calif.

[0048]FIG. 7 depicts one embodiment of a pre-clean chamber 672.Generally, the pre-clean chamber 672 may be a remote plasma source (RPS)chamber such as the Etch RPS chamber which is also available fromApplied Materials, Inc., of Santa Clara, Calif. Alternatively, aPRE-CLEAN™ II chamber as described above, or a metal CVD/PVD chamberhaving a remote plasma source coupled thereto among other chambers maybe utilized. For example, gas inlets could be provided at the level ofthe substrate in the metallization chambers to deliver the reactive gasplasma or hydrogen plasma from the remote plasma source. Metaldeposition chambers having gas delivery systems could be modified todeliver the pre-cleaning gas plasma through existing gas inlets such asa gas distribution showerhead positioned above the substrate.

[0049] The pre-clean chamber 672 generally includes two majorassemblies: 1) a chamber body, including an electrostatic chuck whichsupports and secures a substrate in the chamber; and 2) a remote plasmasource. These major assemblies will be discussed separately for the sakeof organization, although it will be understood that in reality there isdynamic interaction between these assemblies. In a RPS chamber, reactiveH radicals are formed and are primarily neutral species preventinggeneration of self bias and bombardment of the wafer surface by ions.Experiments with RPS chambers show that a 2.45 GHz microwave source ismore efficient and can generate more hydrogen ions than lower frequencyRF sources.

[0050] The pre-clean chamber 672 generally includes a chamber body 716having a slit valve port 718 which connects the chamber 672 to thesubstrate processing system 660, such as an ENDURA® platform. A fixedcathode 712, which includes an electrostatic chuck 714 that secures thesubstrate (not shown) to the fixed cathode 712, is disposed within thechamber body 716.

[0051] The fixed cathode 712 is shielded from process gases by a cathodeliner 720 that has a non-stick outer surface to enhance processperformance. The chamber body 716 is also shielded from process gases bya chamber liner 722 which has a non-stick inner surface to enhanceprocess performance. The chamber liner 722 includes an inner annularledge 724 that supports a gas distribution plate 726. The gasdistribution plate 726 has a plurality of spaced holes that distributeprocess gases over the surface of the substrate positioned on theelectrostatic chuck 714.

[0052] A processing region 730 above the fixed cathode 712 is maintainedat a low process pressure by vacuum pumps (not shown) which are in fluidcommunication with an exhaust port 732 on the chamber body 716. A baffleplate 734 having a plurality of spaced holes separates the processingregion 730 from the exhaust port 732 to promote uniform exhaustingaround the fixed cathode 712. The processing region 730 is visible fromoutside the chamber 672 through a sapphire window 736 that is sealed inthe chamber body 716.

[0053] The chamber body 716 has a removable chamber lid 740 that restson the chamber liner 722. The chamber lid 740 has a central injectionport 742 that receives process gases from the remote plasma source 750.

[0054] Process gases for the pre-cleaning process are excited into aplasma within the remote plasma source 750 which is in fluidcommunication with the chamber body 716 described above. A plasmaapplicator 752 has a gas inlet 754 that receives process gases. Theprocess gases flow through the applicator 752 and exit into the centralinjection port 742 in the chamber lid 740. A jacket waveguide 756surrounds a sapphire tube portion of the plasma applicator 752 andsupplies microwave energy to the process gases.

[0055] Microwave energy is generated by a magnetron 760 that provides upto 1500 watts at 2.45 GHz. The microwave energy passes through amicrowave isolator 762 that prevents reflected power from damaging themagnetron 760. The microwave energy from the isolator 762 is transmittedthrough a waveguide 764 to an autotuner 766 that automatically adjuststhe impedance of the plasma in the applicator 752 to the impedance ofthe magnetron 760 thus resulting in minimum reflected power and maximumtransfer of power to the plasma applicator 752.

[0056] In configurations where a metal CVD/PVD chamber having a remoteplasma source coupled thereto is utilized, gas inlets typically areprovided at the level of the substrate in the metallization chambers todeliver the reactive gas plasma or hydrogen plasma from the remoteplasma source. Metal deposition chambers having gas delivery systemscould be modified to deliver the pre-cleaning gas plasma throughexisting gas inlets such as a gas distribution showerhead positionedabove the substrate.

[0057] Returning to FIG. 6, the substrate is typically processed in theprocessing system 660 by transferring the substrate from the cassetteloadlock 662 to the buffer chamber 668 where the robot 664 first movesthe substrate into a degas chamber 670. After degas, the substrate isthen transferred into the pre-clean chamber 672. After removal of nativeoxides and other contaminants, the substrate is transferred to the PVDHP TiN chamber 675 for barrier layer deposition, and then into acooldown chamber 676. From the cooldown chamber 676, the robot 678typically moves the substrate into and between one or more processingchambers before returning the substrate back to a cooldown chamber 676.It is anticipated that the substrate may be processed or cooled in oneor more chambers any number of times in any order to fill the submicronfeatures with aluminum or other materials. The substrate is removed fromthe processing system 660, following processing, through the bufferchamber 668 and then to the loadlock 662.

[0058] The processing system 660 passes a substrate through loadlock 662into de-gas chamber 670 wherein the substrate is introduced to out gascontaminants. A substrate is then moved into the remote plasma sourcepre-clean chamber 672 where the submicron features are cleaned to removeany contaminants thereon and to reduce native oxides. The substrate isthen processed in the PVD HP Ti/TiN chamber 675 to deposit a Ti/TiNbarrier layer on the cleaned dielectric surfaces, and then passed to acooldown chamber 676. The second robot 678 then transfers the substrateto one or more CVD and PVD chambers for deposition of aluminum, copperor other materials.

[0059] Another application of the integrated platform of FIG. 6 providesfor copper deposition by providing a CVD TiN chamber 675, a PVD Cuchamber 682, a CVD Cu chamber 684, a PVD HTHU Cu chamber 686, and a PVDIMP Ta/TaN chamber 688. The substrate is processed in the CVD TiNchamber 675 or PVD IMP Ta/TaN chamber 688 to deposit a CVD TiN or Ta/TaNbarrier layer on the cleaned dielectric surfaces, and then the substrateis passed to a cooldown chamber 676. Pre-cleaning of submicron featuresprior to copper deposition can be performed in the pre-clean chamber 672or in a PRE-CLEAN™ chamber as described above which replaces a cooldownchamber 676. The second robot 678 then transfers the substrate to one ormore CVD and PVD chambers for copper deposition. Deposited Cu layers maybe annealed with H₂ to make the layer more resistant to formation ofCuO.

[0060] Another application of the integrated platform 660 provides fortungsten deposition by providing a IMP Ti chamber, two CVD TiN chambers,and two pre-clean chambers. The substrate is processed in the IMP Ti andCVD TiN chambers to deposit Ti/TiN barrier layers on the cleaneddielectric surfaces, and then the substrate is passed to a cooldownchamber.

[0061] A staged-vacuum wafer processing method suitable for use with thepresent invention is disclosed in U.S. Pat. No. 5,186,718, entitledStaged-Vacuum Wafer Processing System and Method, issued Feb. 16, 1993to Tepman et al., and is hereby incorporated herein by reference. Thismethod readily accommodates the pre-cleaning method of this invention.Any combination of processing chambers can be used with the dedicatedpre-cleaning chamber.

[0062] While the foregoing is directed to the preferred embodiment ofthe present invention, other and further embodiments of the inventionmay be devised without departing from the basic scope thereof. Forexample, native oxides and other contaminants may be removed from layersother than copper. The scope of the invention is determined by theclaims that follow.

What is claimed is:
 1. A method for monitoring a process of removingnative oxides from an at least partially exposed layer disposed on asubstrate, the method comprising: disposing the substrate in a processchamber; exposing the at least partially exposed layer to a reactivepre-clean process; removing the substrate from the process chamber; andmeasuring a sheet resistance of the exposed layer.
 2. The method ofclaim 1, wherein the step of measuring the sheet resistance furthercomprises: contacting the at least partially exposed layer with at leastone probe set, the probe set comprising two or more contact memberscoupled to a resistance meter.
 3. The method of claim 1, wherein thestep of measuring the sheet resistance further comprises: contacting theat least partially exposed layer with a plurality of probe sets, eachprobe set comprising two or more contact members disposed in aspaced-apart relation.
 4. The method of claim 3, wherein the step ofcontacting the exposed layer further comprises: contacting the exposedlayer with a first group of probe sets; and contacting the exposed layerwith a second group of probe sets disposed radially outward from thefirst group of probe sets.
 5. The method of claim 3, wherein the step ofmeasuring the sheet resistance further comprises: comparing the measuredresistance between the first and second groups of probe sets.
 6. Themethod of claim 3, wherein the step of measuring the sheet resistancefurther comprises: averaging the measured resistance.
 7. The method ofclaim 1 further comprising: comparing the measured sheet resistance to asheet resistance known for the at least partially exposed layer.
 8. Themethod of claim 1, wherein the reactive pre-clean process comprises:forming a plasma from a gas comprising an inert carrier gas combinedwith less than about 5 percent hydrogen; and reducing native copperoxide from the at least partially exposed layer.
 9. The method of claim8, wherein the reactive pre-clean process further comprises: inductivelycoupling about 1 to about 1000 Watts to the plasma; and biasing asubstrate support with less than about 100 Watts.
 10. A method formonitoring a process of removing native oxides from an at leastpartially exposed conductive layer disposed on a substrate, the methodcomprising: disposing the substrate in a process chamber; exposing theat least partially exposed conductive layer to a reactive pre-cleanprocess that comprises an oxide reduction step; removing the substratefrom the process chamber; contacting the conductive layer with two ormore contact members; measuring a sheet resistance of the exposedconductive layer between the contact members; and comparing the measuredresistance to a known value.
 11. The method of claim 10, wherein thestep of contacting the at least partially exposed conductive layerfurther comprises: contacting the exposed conductive layer with at leastone probe set, the probe set comprising two or more contact memberscoupled to a resistance meter.
 12. The method of claim 10, wherein thestep of contacting the exposed layer further comprises: contacting theexposed conductive layer with a first group of probe sets; andcontacting the exposed conductive layer with a second group of probesets disposed radially outward from the first probe set.
 13. The methodof claim 10, wherein the step of measuring the sheet resistance furthercomprises: comparing the measured resistance between the first andsecond groups of probe sets.
 14. The method of claim 10, wherein thestep of measuring the sheet resistance further comprises: averaging themeasured resistance.
 15. The method of claim 10, wherein the reactivepre-clean process comprises: forming a plasma from a gas comprising aninert carrier gas combined with less than about 5 percent hydrogen; andreducing native copper oxide from the exposed conductive layer.
 16. Themethod of claim 15, wherein the reactive pre-clean process comprises:inductively coupling about 1 to about 1000 Watts to the plasma; andbiasing the substrate support with less than about 100 Watts.
 17. Themethod of claim 10, wherein the conductive layer is aluminum or copper.18. A method for monitoring a process of removing native copper oxidefrom an at least partially exposed copper layer disposed on a substrate,the method comprising: disposing the substrate in a process chamber;exposing the at least partially exposed copper layer to a reactivepre-clean process that comprises exposing the copper oxide to a plasmaformed from a hydrogen comprising gas; removing the substrate from theprocess chamber; contacting the exposed copper layer with two or morecontact members; measuring a sheet resistance of the exposed copperlayer between the contact members; and comparing the measured resistanceto a known value.
 19. A method for monitoring a process of removingnative oxides from an at least partially exposed conductive layerdisposed on a substrate, the method comprising: exposing the exposedconductive layers to a plasma at least partially formed from hydrogen ina first chamber coupled to a processing platform to remove native oxidesfrom the exposed conductive layer; transferring at least one of a seriesof substrates exposed to the plasma from the first chamber to ametrology device; measuring the sheet resistance of the conductivelayer; and comparing the measured sheet resistance to a known value. 20.The method of claim 19, wherein the measured substrate is one of aseries of production substrates being processed.
 21. The method of claim19, wherein the measured substrate is a utility substrate.
 22. Themethod of claim 19, wherein the step of measuring the sheet resistancefurther comprises: contacting the exposed layer with at least one probeset, the probe set comprising two or more contact members coupled to aresistance meter.
 23. The method of claim 22, wherein the step ofcontacting the exposed layer further comprises: contacting the exposedlayer with a first group of probe sets; and contacting the exposed layerwith a second group of probe sets disposed radially outward from thefirst probe set.
 24. The method of claim 19, wherein the step ofmeasuring the sheet resistance further comprises: comparing the measuredresistance between the first and second groups of probe sets.
 25. Themethod of claim 19, wherein the step of measuring the sheet resistancefurther comprises: averaging the measured resistance.
 26. The method ofclaim 19, wherein the reactive pre-clean process comprises: forming aplasma from a gas comprising an inert carrier gas combined with lessthan about 5 percent hydrogen; and reducing native copper oxide from theexposed layer.
 27. The method of claim 26, wherein the reactivepre-clean process comprises: inductively coupling about 1 to about 1000Watts to the plasma; and biasing a substrate support with less thanabout 100 Watts.